Large scale optical phased array

Abstract

Aspects of the present disclosure describe configurations of, and methods for operating a large-scale optical phased array for contemporary applications including LIDAR, optical communications, imaging, and displays—among others.

The invention claimed is: 
     
       1. An optical phased array structure comprising:
 an optical source; 
 an array of phase-controlled elements, said array of phase-controlled elements grouped into individually phase-controlled sub-arrays of the phased-controlled elements, and each of the individually phase-controlled sub-arrays associated with a respective sub-array phase shifter; and 
 an optical distribution network comprising: (1) a source sub-network configured to optically connect the optical source with an input of each of the sub-array phase shifters, and (2) a plurality of sub-trees configured to optically connect respective sub-array phase shifters with a plurality of the phase-controlled elements; 
 wherein each sub-tree of the optical distribution network is equal-sized such that optical paths from each phase-controlled element to a root of each sub-tree are substantially equal for each sub-tree. 
 
     
     
       2. The optical phased array structure of  claim 1  wherein the phase-controlled elements of the array of phase-controlled elements are all individually phase-controlled elements of an array of individually phase-controlled elements. 
     
     
       3. The optical phased array structure of  claim 2  wherein the individually phased-controlled elements included in the individually phase-controlled sub-arrays are contiguous members of the array of individually phase-controlled elements. 
     
     
       4. The optical phased array structure of  claim 2  wherein each of the individually phase-controlled elements of the array of individually phase-controlled elements includes a respective element phase shifter optically connected with an optical emitter. 
     
     
       5. The optical phased array structure of  claim 4  wherein the element phase shifters are configured to shift within a range of 2π. 
     
     
       6. The optical phased array structure of  claim 4  wherein at least one of the element phase shifters is one selected from the group consisting of: thermo-optic, electro-optic, mechanical, fluidic, liquid crystal, non-linear, acousto-optic, and stress-induced phase shifters. 
     
     
       7. The optical phased array structure of  claim 4  wherein the optical emitter is one selected from the group consisting of: an optical grating, end-fire facet, plasmonic emitter, metal antennae, and mirror facet. 
     
     
       8. The optical phased array structure of  claim 4 , wherein respective ones of the individually phase-controlled elements of the individually phase-controlled sub-arrays are collectively phase-controlled such that an optical phased array having N individually phase-controlled elements, grouped into sub-arrays that each consist of G individually phase-controlled elements, uses approximately S=N/G+G control signals for controlling all of the sub-array phase shifters and element phase shifters, where G is approximately equal to the square root of N. 
     
     
       9. The optical phased array structure of  claim 4  wherein the number of phase-controlled elements included in an individually phase-controlled sub-array is determined based at least in part on: a number of ports providing control signals for controlling all of the sub-array phase shifters and element phase shifters; and an operating speed required of a respective sub-array phase shifter. 
     
     
       10. The optical phased array structure of  claim 2  configured to output an overall optical phase front, wherein each one of the individually phase-controlled sub-arrays is configured to output an optical phase front that is a modulo 2π of the overall optical phase front. 
     
     
       11. The optical phased array structure of  claim 2  wherein each of the individually phase-controlled elements of the array of individually phase-controlled elements includes a respective element phase shifter optically connected with an optical emitter, and at least one of the element phase shifters and at least one of the sub-array phase shifters are not the same type of phase shifter wherein the phase shifter type is one selected from the group consisting of: thermo-optic, electro-optic, mechanical, fluidic, liquid crystal, non-linear, acousto-optic, and stress-induced phase shifters. 
     
     
       12. The optical phased array structure of  claim 2 , wherein selected ones of the individually phase-controlled elements of selected individually phase-controlled sub-arrays are collectively phase-controlled. 
     
     
       13. The optical phased array structure of  claim 2  arranged in a dimension selected from the group consisting of: 2-dimensional array, and 3-dimensional array. 
     
     
       14. The optical phased array structure of  claim 1  wherein the optical distribution network has a 1×N splitter topology and said source sub-network optically connects each individually phase-controlled sub-array to the optical source with a structure selected from the group consisting of: binary tree, star coupler, 1×M splitter network where M<N, directional coupler, free space structures, and slab waveguides. 
     
     
       15. The optical phased array structure of  claim 1  wherein each of the individually phase-controlled sub-arrays is associated with a respective sub-array phase shifter assembly, said respective sub-array phase shifter assembly including more than one individual sub-array phase shifter configured to operate as a set. 
     
     
       16. The optical phased array structure of  claim 15 , wherein the respective sub-array phase shifter assembly is positioned in an optical path after another phase shifter in the optical path. 
     
     
       17. An optical phased array structure comprising:
 a plurality of array elements, each individual one of the plurality of array elements including a respective element phase shifter optically connected with an emitter; and 
 said plurality of array elements configured as a plurality of sub-phased arrays, each individual one of the plurality of sub-phased arrays further including a phase residue phase shifter; 
 wherein respective ones of the array elements of the sub-phased arrays are collectively phase-controlled such that an optical phased array having N array elements, grouped into sub-phased arrays that each consist of G array elements, uses approximately S=N/G+G control signals for controlling all of the residue phase shifters and element phase shifters, where G is approximately equal to the square root of N. 
 
     
     
       18. The optical phased array structure of  claim 17  wherein more than one of the sub-phased arrays are further grouped into a sub-sub-phased array. 
     
     
       19. The optical phased array structure of  claim 17  further comprising:
 an optical source; and 
 an optical distribution network configured to optically connect the optical source with an input of each of the sub-phased arrays. 
 
     
     
       20. The optical phased array structure of  claim 17  wherein the number of array elements included in a sub-phased array is determined based at least in part on: a number of ports providing control signals for controlling all of the phase residue phase shifters and element phase shifters in the optical phased array; and an operating speed required of a respective phase residue phase shifter.